Assessment of heavy metal concentration in vegetables grown around Jakara Reservoir, Kano State Nigeria

Abstract

Heavy metal concentrations in vegetables (onion, pepper, and tomatoes) were used to evaluate the pollution state of Jakara Reservoir in Kano State between February and May of 2024. Analysis of the heavy metals was done according to established procedure. Every month, vegetables were gathered from six sampling locations designated A, B, C, D, E, and F according to the different human activity surrounding the reservoir. The findings showed that onion samples had mean values for Copper (Cu), Cadmium (Cd), Chromium (Cr), Manganese (Mn), Nickel (Ni), Lead (Pb), and Cobalt (Co) of 0.93, 0.37, 1.01, 0.79, 0.81, 0.69, and 0.56 mg/kg, respectively. Onions had the lowest levels of Cd while the highest level was Cr. The heavy metal accumulation in onions was as follows: Cr > Cu > Ni > Mn > Pb > Co > Cd. The following elements were found in pepper: Pb, Co, Mn, Ni, Cu, (Cr), (Cd), and 0.76, 0.66, 1.61, 0.58, 0.54, 0.53, and 0.48 mg/kg, respectively. Pepper accumulated in the following decreasing order: Cr > Pb > Cd > Mn > Cu > Ni > Co with the exception of Ni and Mn. The concentrations of all the heavy metals in pepper were higher than the FAO's recommended limit (2020). Tomatoes had correspondingly values of 0.63, 0.61, 0.49, 0.44, 0.29, 0.28, and 0.25 mg/kg of Cu, Cr, Cd, Mn, Ni, Co, and Pb. Cu > Cr > Cd > Ni > Mn > Co > Pb was the decreasing order for metals in tomatoes. With the exception of Cr, Mn, and Ni, the concentrations of all heavy metals in tomatoes were higher than the FAO's recommended level (2020). Based on the current study's findings, it can be said that eating vegetables grown in the study area poses a serious risk to the consumer's health. As a result, it is advised that the appropriate authorities enforce the safety regulations pertaining to vegetables originating from the research region and suggest alternate irrigation areas where the vegetables can be produced using uncontaminated soil.